Protective device for electrical precipitators



2 Sheets-Sheet 1 A. N. CROWDER PROTECTIVE DEVICE FOR ELECTRICAL PRECIPITATORS Filed March 7, 1947 .7"!!!IIIIIIIIIIIIIIIIH May 9, 1950 I N V EN TOR. A [e xander' N. Crowder.

l l/ III/ffflIl/lIl/l/lllfrlllllfll/l/ I! May 9, 1950 A. N. CROWDER PROTECTIVE DEVICE FOR ELECTRICAL PRECIPITATORS 2 Sheets-Sheet 2 Filed March 7, 1947 INVENTOR. Alexander/V. Cr owder Patented May 9, 1950 UNITED STATES PATENT OFFICE Somerset County, N. J., assignor to Research Corporation, New York, N. Y., a corporation of New York Application March 7, 1947; Serial N 0. 733,148

9 Claims.

inventionrelates to electrical precipitators having a protective device for preventing damage to the high tension discharge wires of the precipitator.

Angbject of the invention is to provide, in an electrical precipitator having high tension discharge electrodes spaced from collecting electrode surfaces in a dust collecting chamber, a sparking terminalinsulated in the dust collecting chamber andpoisitioned below the discharge electrodes and connected through a low resistance conductor to the frame supporting the discharge electrodes, whereby to provide a safety circuit of low resistance in parallel with the high tension electrode wires. In the event that dust is inadvertently allowedto pile up in the collector to a height approaching the lower ends of the high tension wires-a condition normally conducive to sparkover.,between the wires and the dust pile with attendant danger of burning the wires-the sparking terminal and supplemental circuit of the invention will safely conduct any dangerous current surges which occur until action can be taken to eliminate the sparking.

Another object is to provide a simple, effective, and inexpensive sparking terminal device that can be readily attached to existing electrical precipitator installations for efiecting the desired protection. I

In a typical embodiment, the invention includes, in an electrical precipitator having verticallyextending high tension discharge electrodes ofylow conductivity, complementary extended surface collecting electrodes, a dust receiver positioned below said electrodes, the lower ends of said high tension electrodes depending into said dust receiver, and means having high conductivity supplying high tension current to the upper ends of said disohargeelectrodes; a sparking terminal insulatedly supported in said dust receiver below the bottoms of said high tension electrodes; and low. resistance conductor means connecting said sparking terminal to said means supplying high tension current to said discharge electrodes.

The; sparking terminal device of the invention is particularly adapted to 'beattached to the lower irame'member of an electrical precipitator having vertically extending discharge electrodes, a dustreceiver positioned below said-electrodes, the discharge electrodes depending into said dust receiver,,gand an insulated conductive discharge electrode support including an upper horizontal frame member from which said velectrodes are suspended, and a lower horizontal frame member providing guides through which said electrodes r 2 depend, and means for connecting a soil-et er high tension current to said electrode support; The sparking terminal device includes an elongated member of high mechanical strength and electrical conductivity and means for electrically and mechanically connecting said member to the lower frame member of the discharge electrode support. The sparking terminal device may also include a separate conductor of low resistance connected thereto and to the upper frame memberof the discharge electrode support. H i

The principles of the invention willbe set for'th with greater particularity in the following de; tailed description taken in connection with the accompanying drawings, wherein: V H L M Fig, 1 is a horizontal sectionalview, taken along the plane of the line I-i of Fig. '2, of an elec trical precipitator including sparking terminals in, accordance with'the invention; V V H w Fig. 2 is a vertical sectional view taken along the plane-of the line 2-2 of Fig.1; 7

Fig. 3 is an enlarged detail side view of one of the sparking terminal devices of the inventions Fig. 4 is a fragmentary detail view of ainodified form of the invention; and r Fig. 5 is a fragmentary detail view of still'a-nother modification. I v

Referring to the drawings, particularly to Figs. 1 and 2 thereof, there is shown-an electrical precipitator having a casing i0 defining a precipitat ing chamber I l having a gas inlet conduit I2 and,

a gas outlet conduit 13, gas flow through the apparatus being in the directional sense of the arrow shown in the figures. Directly below and. communicating with the precipitating chamber is a dust receiver l4 in the form of ahopper having a dust removal opening (not show-n)- at the bottom. As is conventional, dust removed;

from the gas stream in the precipitating chamber falls into the hopper from which it is removed, from time to time, as necessary.

Opposed, spaced, complementary electrodesare positioned in the chamber 5 i. The extendedsurface or collecting electrodes l5 are shown specifically as vertically extending, spaced, parallel,

metallic, plates positioned parallel to the-gas stream flow and supported in the casing Ill bybrackets [6. These collecting electrodes preferably are at least coextensive with the vertical dimension of the gas stream flowingthroug-h the apparatus and project somewhat into the 'dea'dair space of the hopper M at their lower edges; and, at their upper edges, somewhat into dead-air space"! i at the top of'the'casi'ng l0.

Gomplementary high tension electrodes; "ion.

example fine wires l8, are disposed to form ourtains adjacent to the faces of the collecting electrodes. These high tension electrodes function in the usual manner in conjunction with the extended surface electrodes to provide corona or brush discharge and electric precipitating fields when a suitable high potential is maintained across the complementary electrodes. Dust particles suspended in the gas stream passing between the electrodes are charged and precipitated upon the collecting electrodes I5. The precipitated dust is removed from the electrodes l5, as by rapping the electrodes, and falls into the hopper I4.

The high tension electrodes are carried by a support generally-designated IS. The support is conveniently fabricated from pipe and pipe fittings and includes an upper frame member and a lower frame member 21 joined together to form a rigid cage-like structure by vertically extending pipes 22. The pipe elements of the structure may be flattened to render them eliptical, the major axes of the eliptical sections being disposed in planes parallel to the collecting electrodes IE to present to the collecting electrodes pipe surfaces of relatively large radius of curvature for the purpose of minimizing any tendency for disruptive discharge to occur between the pipes and the collecting electrodes.

The high tension electrode support i 9 is rigidly suspended from the roof of the casing, being carried by pipe elements 23 and 24 mounted in insulators 25 and insulating bushing 26 affixed to the roof.

A conventional source of high tension current,

diagrammatically shown at 21, has one terminal connected to the pipe element 24 through conductor 28 and the other terminal connected to the casing It and to ground through conductor 29.

The high tension electrode wires 18 are suitably attached to the longitudinal bars 30 of the upper frame member, extend downwardly through holes in the longitudinal bars 3i of the lower frame member, and have weights 32 attached to their lower ends. The wires pass freely through the holes in bars 3! so that, in effect, they hang from the upper bars 38. In this construction, the lower frame member 2i serves to steady the wires and hold them in proper position.

Ido'rder to eliminate spark-over between the edges of the electrode plates i5 and the wires "3, the usual shrouds 33 may be provided at the top and bottoms of the wires.

The specific electrical precipitator thus far described may be considered more or less conventional. It is subject to the objection that, if dust is allowed to accumulate in the receiver l4 until the surface of the dust pile approaches closely the bottoms of the weights 32, sparking will occur across the gap between the bottoms of the weights and the top of the dust pile. Under such circumstances, current surges through the wires causing the latter to burn out in a short time. The burning is usually the result of small discharges, so-called spit arcs, which occur between the discharge wire and. an adjoining surface which is not bonded tightly to the wire, as where the wire passes freely through a hole in the steadying frame or through a shroud.

Means in accordance with the invention for obviating the foregoing objection may take a variety of forms, one of which is shown in Figs. 1 and 2. In this modification, sparking terminals or contact devices 34 are firmly attached to the ill . 4 steadying frame 2| at points where experience has shown that dust may pile up in the receiver to a dangerous height. Such points are often near the sides of the dust receiver, as indicated by the showing in Fig. 2 of the body of dust 35. The sparking terminals are low resistance metallic members which project below the bottoms of the weights 32. They make good electrical contact with the pipes of the lower frame members 2|. It will be seen that, as dust rises in the hopper, sparking will first occur between the sparking terminals 34 and the dust pile. Current surges occasioned thereby will flow preferentially through the low resistance pipe members of the high tension electrode support l9 and will not damage or burn the high tension wires 18. Such sparking is relatively harmless; it is quickly noted by the operator who can take immediate action to empty the hopper I4 before the dust rises therein to a dangerous level.

Fig. 3 shows, in enlarged detail, the construction of one of the sparking terminals. In this figure, pipe 3! serves as a support for the contact point 35. Strap 36 is made to fit over the upper surface of pipe 31 and it clings tightly to the latter when the ends of the strap are pulled together by bolt 3'!. The bolt has a rounded head 38 on the side that is placed next to the surfaces of hopper 4 to eliminate sparking tendency, and a conventional nut 39 is screwed on the other end. The ends of the strap are bent to encompass a portion of the surface of rod 35 to hold it in vertical position. Bolt 3! passing through a hole in rod 35 near the upper end thereof gives the latter additional support. Bolt 31 can usually be depended upon to provide satisfactory mechanical and electrical connections between the parts, but welding can be resorted to after the positioning of the sparking terminal or terminals has been decided upon. A heavy wire conductor 48 may be connected to a satisfactory conducting member located at a distance if the members immediately adjacent to the terminal do not provide adequate electrical conductance.

Fig. 4 shows a modification of the invention. A bar, or series of parallel bars 4| depend below the tensioning weights 32, being supported by attachment to the steadying frame 2| by means of pipe extensions 42. The bar or bars 4! are placed in positions where they will contact the dust as it rises in the hopper before it reaches the weights. Commonly, this position or region is around the perimeter of the hopper at such distance in from the hopper walls that electrical discharges between the bars and the walls will' not take place. Contact points 43 can also be used with this bar if conditions indicate that benefit will result from their use.

Fig. 5 shows in perspective still another modified form of the invention. The angular bar 44 is attached at its elbow as by welding to a vertical bar 65 which is threaded or otherwise adapted for fastening to coupling member 46 of the lower steadying frame 2!. Angular bars as illustrated in Fig. 5 can be placed at each corner of the lower steadying frame or at those corners only where experience shows that high levels of dust can be expected.

From the foregoing description it will be seen that the present invention provides means in an electrical precipitator for effectively preventing burning of the high tension electrode wires, where the wires or tensioning weights attached thereto are likely to come in contact with a rising pile of dust.

I claim:

1. In an electrical precipitator having vertically extending high tension discharge electrodes of low conductivity, complementary extended surface collecting electrodes, a dust receiver positioned below said electrodes, the lower ends of said high tension electrodes depending into said dust receiver, and means supplying high tension current to the upper ends of said high tension electrodes; a sparking terminal supported. in said dust receiver below the bottoms of said high tension electrodes; and means for adjusting the position of said sparking terminal with respect to the bottoms of said high tension electrodes, said sparking terminal being electrically connected to said high tension current supply means through a conductive path of low resistance.

2. In an electrical precipitator having vertically extending high tension discharge electrode wires of low conductivity, complementary extended surface collecting electrodes, a dust receiver positioned below said electrodes, the lower ends of said high tension electrode wires depending into said dust receiver, and means supplying high tension current to the upper ends of said high tension electrode wires; a sparking terminal supported in said dust receiver below the bottoms of said high tension electrode wires; and means for adjusting the position of said sparking terminal with respect to the bottoms of said high tension electrodes, said sparking terminal being electricallly connected to said high tension current supply means through a conductive path of low resistance.

3. In an electrical precipitator including com plementary extended surface and high tension discharge electrodes, a high tension electrode support frame positioned above said electrodes, said high tension discharge electrodes being mechanically suspended from and electrically connected to said frame, means for connecting a source of high tension current to said frame, and a dust receiver positioned below said electrodes; a sparking terminal supported in said dust receiver below the lower ends of said high tension discharge electrodes, and means for adjusting the position of said sparking terminal with respect to the bottoms of said high tension electrodes, said sparking terminal being electrically connected to said high tension current supply means through i a conductive path of low resistance.

4. In an electrical precipitator including complementary extended surface and high tension discharge electrodes, a high tension electrode support frame positioned above said electrodes,

said high tension discharge electrodes being mechanically suspended from and electrically connected to said frame, means for connecting a source of high tension current to said frame, a high tension electrode steadying frame, means rigidly suspending said steadying frame from said support frame in position to embrace the lower ends of said discharge electrodes, said steadying frame being relatively highly conductive and being electrically connected to said support frame through said suspending means, and a dust receiver positioned below said lectrodes; a sparking terminal positioned in said dust receiver below the lower ends of said high tension discharge electrodes, and means adjustably mounting said sparking terminal on said steadying frame, said sparking terminal being electrically connected to said steadying frame.

5. In an electrical precipitator including complementary extended surface and high tension electrodes, a high tension electrode support frame positioned above said electrodes, said high tension discharge electrodes being mechanically suspended from and electrically connected to said frame, means for connecting a source of high tension current to said frame, a conductive high tension electrode steadying frame, means rigidly suspending said steadying frame from said support frame in position to embrace the lower ends of said discharge electrodes, said steadying frame being electrically connected to said support frame through said suspending means, and a dust receiver positioned below said electrodes; a horizontal conductive bar positioned in said dust receiver below the lower ends of said discharge electrodes; and means mechanically and electrically connecting said bar to said steadying frame.

6. In an electrical precipitator as defined in claim 5, a sparking terminal electrically and mechanically connected to and projecting downwardly from said bar.

7 A sparking terminal for electrical precipitators comprising an elongated conductive member of relatively high mechanical strength, said member being pointed at its lower end and having a transverse hole near its upper end, a U-shaped metallic strap inverted over the upper end of said member, the arms of said strap embracing the sides of said member and providing holes in alignment with said transverse hole, and a bolt passing through said holes.

8. A sparking terminal for electrical precipitators comprising an elongated conductive member of relatively high mechanical strength, said member being pointed at its lower end and having a transvers hole near its upper end, a U-shaped metallic strap inverted over the upper end of said member, the arms of said strap embracing the sides of said member and providing holes in alignment with said transverse hole, a bolt passing through said holes, and a flexible conductor fastened to said bolt.

9. A sparking terminal for electrical precipitators including a lower steadying frame comprising an L-shaped conductive member of relatively high mechanical strength, a straight conductive member of relatively high mechanical strength attached to said L-shaped member at the angle thereof and extending normally to the plane thereof, and means for attaching said straight member to the steadying frame of the precipitator.

ALEXANDER N. CROWDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,462,346 Kline July 17, 1923 1,541,677 Anderson June 9, 1925- 2,018,672 Hill Oct. 29, 1935 FOREIGN PATENTS Number Country Date 428,471 Great Britain May 14, 1935 

